Sex differences in muscle activation during inclined leg press exercise: Effects of stance width, load, and contraction phase

Abstract

Background: Training safely is important for maintaining healthy locomotion and thus high quality of life into the later years. There is a dearth of information on the sex differences of performing different weight training techniques. Objective: This study aimed to investigate sex differences in lower limb muscle activation during inclined leg press exercise under three biomechanical conditions: (1) stance width (standard vs. wide), (2) load intensity (30% vs. 70% 1RM), and (3) contraction phase (concentric vs. eccentric). A secondary objective was to explore within-sex differences in muscle activation patterns across these conditions. Methods: For this study we recruited 18 healthy young adults (male: 9, female: 9) and each participant performed inclined leg press in two stance conditions (standard and wide) at two load conditions (30% and 70% of the estimated 1 repetition maximum). Muscle activation of six major muscles of the dominant leg was measured by electromyography and normalized integrated EMG (% IEMG) was calculated. A significant level of P<0.05 was applied to investigate any statistical differences. Results: Muscular activation in males tends to be greater during wide stance than standard whereas no such effect of stance was observed in females. The change in stance from standard to wide, significantly increased activation of vastus medialis muscles only in males at higher loads. The increase in load significantly increased muscle activation of vastus lateralis in a wide stance in both groups. Conclusions: In this study we specified the differences in muscle activation between women and men which can provide a guideline for maximizing muscular stimulation and reducing sex specific joint loading.